title: Microvascular biodistribution of L19-SIP in angiogenesis targeting strategies.
abstract: BACKGROUND
  Various strategies using L19-mediated fibronectin targeting have become useful clinical tools in anti-tumour therapy and diagnostics. The aim of our study was to characterise the microvascular biodistribution and binding process during tumour angiogenesis and after anti-angiogenic therapy.
  
  
  METHODS
  SF126 glioma and F9 teratocarcinoma cells were implanted into dorsal skin fold chambers (SF126: n = 4; F9: n = 6). Using fluorescence and confocal intravital microscopy the biodistribution process was assessed at t = 0 h, t = 4 h and t = 24 h after intravenous application of Cy3-L19-SIP. Sunitinib treatment was applied for six days and microscopy was performed 2 and 6 days after treatment initiation. Analysed parameters included: vascular and interstitial binding, preferential binding sites of L19-SIP, microvascular blood flow rate, microvascular permeability. Histological analysis included CD31 and DAPI.
  
  
  RESULTS
  L19-SIP showed a specific and time-dependent neovascular binding with a secondary extravasation process reaching optimal vascular/interstitial binding ratio 4 hours after iv administration (F9: L19-SIP: vascular binding: 74.6 ± 14.5; interstitial binding: 46.8 ± 12.1; control vascular: 22,2 ± 16.6). Angiogenic sprouts were preferred binding sites (F9: L19-SIP: 188 ± 15.5; RTV: 90.6 ± 13.5). Anti-angiogenic therapy increased microvascular hemodynamics (SF126: Su: 106.6 ± 13.3 μl/sec; Untreated: 19.7 ± 9.1 μl/sec) and induced increased L19-SIP accumulation (SF 126: t24; Su: 92.6 ± 2.7; Untreated: 71.9 ± 5.9) in therapy resistant tumour vessels.
  
  
  CONCLUSIONS
  L19-SIP shows a time and blood-flow dependent microvascular biodistribution process with angiogenic sprouts as preferential binding sites followed by secondary extravasation of the antibody. Microvascular biodistribution is enhanced in anti-angiogenic-therapy resistant tumour vessels.
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Charitè, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Czabanka
authors.forename: Güliz
authors.initials: G
authors.lastname: Parmaksiz
authors.forename: Simon H
authors.initials: SH
authors.lastname: Bayerl
authors.forename: Melina
authors.initials: M
authors.lastname: Nieminen
authors.forename: Eveline
authors.initials: E
authors.lastname: Trachsel
authors.forename: Hans D
authors.initials: HD
authors.lastname: Menssen
authors.forename: Ralf
authors.initials: R
authors.lastname: Erber
authors.forename: Dario
authors.initials: D
authors.lastname: Neri
authors.forename: Peter
authors.initials: P
authors.lastname: Vajkoczy
mesh_terms: D000818:Animals; D000906:Antibodies / Q000737:chemistry*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001932:Brain Neoplasms / Q000098:blood supply / Q000378:metabolism*; D045744:Cell Line, Tumor; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008833:Microcirculation; D018613:Microscopy, Confocal / Q000379:methods; D009389:Neovascularization, Pathologic / Q000473:pathology; D011993:Recombinant Fusion Proteins / Q000737:chemistry*; D018243:Teratocarcinoma / Q000098:blood supply / Q000378:metabolism*
chemical_list: D000906:Antibodies; D000970:Antineoplastic Agents; D011993:Recombinant Fusion Proteins; C513931:SIP(L19) fusion protein